TL;DR
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Two studies presented at the American Academy of Ophthalmology meeting found associations between higher preoperative hemoglobin A1c and complications after cataract or glaucoma surgery. The retrospective findings do not show that lowering A1c before surgery prevents those complications, and researchers say further study is needed.
Two retrospective studies presented at the American Academy of Ophthalmology annual meeting linked higher preoperative hemoglobin A1c levels with complications after eye surgery: cystoid macular edema after cataract surgery and blebitis or endophthalmitis after glaucoma shunt surgery. The results suggest that blood sugar control may help inform preoperative risk discussions, but they do not establish that lowering A1c prevents either complication.
For the cataract analysis, Daniel Fraser, MD, of the University of Minnesota and colleagues examined Veterans Affairs Health System records from 2010 through 2022. They compared 6,808 patients who developed postoperative macular edema within six months of surgery with 121,164 who did not. Across the surgeries studied, the reported incidence of pseudophakic cystoid macular edema was 5.3%.
The rate rose across A1c groups: it was 4.2% for A1c below 6.3% and 6.9% for levels of 8.0% or higher. In the multivariable analysis, diabetic retinopathy was the strongest predictor: it was associated with 3.28 times the odds of postoperative edema, with risk increasing as retinopathy became more severe. Each 1 percentage-point increase in A1c was associated with a 6% increase in the odds of edema.
A separate analysis of glaucoma shunt surgery used the TriNetX clinical research network. After propensity matching, it included 4,182 patients with preoperative A1c below 7.0%, 1,166 with levels from 7.0% to 8.4%, and 777 above 8.4%. The high-A1c group had a five-year hazard ratio of 1.93 for blebitis or endophthalmitis compared with the below-7.0% group. The intermediate group’s risk was not significantly higher. The investigators also reported that pre-existing myopia was associated with increased infection risk, independently of A1c.
A1c Adds Detail to Surgical Risk
The findings could give eye surgeons and patients another factor to discuss before surgery, particularly for people with diabetes or diabetic retinopathy. Fraser said the cataract results support more specific counseling as A1c rises, rather than treating diabetes as a simple yes-or-no risk category. The study found a gradual association with A1c, while also showing that retinopathy had a stronger association with postoperative macular edema.
The glaucoma analysis points to a possible infection concern among patients with A1c above 8.4%, but its confidence interval was wide, and the study was observational. Neither analysis tested whether postponing surgery or changing diabetes management reduces complications. For now, the findings may inform individualized discussions, not a proven A1c threshold for delaying an operation or changing care.
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Two Studies, Different Eye Surgeries
Cystoid macular edema is swelling in the central retina that can affect vision after cataract surgery. Fraser described pseudophakic CME as the most common vision-threatening complication of cataract surgery and said it occurs in up to 4% of surgically treated eyes, while the VA analysis reported a 5.3% incidence in its study population. The figures come from different descriptions and populations, and should not be treated as directly interchangeable.
Earlier, smaller single-center studies had suggested a link between preoperative A1c and macular edema, according to Fraser. The larger VA analysis adds evidence of an association but has limits: it is retrospective, and the VA population is heavily weighted toward older white men. The glaucoma study addressed a different outcome and operation, using a separate data network; its infection findings should not be assumed to apply to cataract surgery.
At the meeting, an audience member cited the European PREMED trial as potentially relevant to preventing CME in patients with diabetic retinopathy. The trial compared no added treatment with subconjunctival triamcinolone, alone or alongside intravitreal bevacizumab. The report said no patients given the corticosteroid developed CME and that bevacizumab added no further effect. That trial considered treatments for retinopathy-associated risk; it did not test whether lowering A1c before surgery changes outcomes.
“I would like to see an interventional study.”
— Daniel Fraser, MD, University of Minnesota
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No Proven A1c Target Before Surgery
The studies show associations, not cause and effect. It remains unknown whether reducing A1c before either operation would lower the chance of macular edema or infection, and the cataract findings do not identify a threshold at which surgery should be delayed. Fraser called for an interventional study to answer whether patients in higher A1c groups benefit from lowering their levels before cataract surgery.
The glaucoma infection estimate also has uncertainty: the high-A1c group’s hazard ratio was 1.93, with a 95% confidence interval from 1.04 to 3.58. The intermediate group did not show a statistically significant increase. The supplied report does not provide the absolute number of infections in each group, limiting interpretation of the estimate in terms of individual patients’ absolute risk. Details of the glaucoma study’s additional comorbidity findings are also incomplete in the available report.
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Trials Could Test Risk Reduction
The next evidence needed is prospective research testing whether an intervention to lower A1c before surgery changes complication rates. Fraser specifically called for such a study in cataract patients, including a test of whether moving patients from higher A1c ranges to lower ones reduces postoperative CME. Until evidence from intervention studies is available, the reported results support risk discussions but do not establish a preoperative A1c target or a reason to delay surgery.
Clinicians will also need to weigh A1c alongside other patient-specific factors. In the cataract study, retinopathy severity was a stronger predictor than A1c; in the glaucoma analysis, myopia was associated with infection risk apart from A1c. The meeting presentations do not report a change to surgical guidelines or a specific recommended management plan.
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Key Questions
What did the cataract surgery study find?
In VA records covering 2010-2022, cystoid macular edema occurred in 4.2% of patients with preoperative A1c below 6.3% and 6.9% of those with A1c of 8.0% or higher. The retrospective study found an association; it did not test whether lowering A1c prevents the complication.
Which factor was the strongest predictor of macular edema?
Preoperative diabetic retinopathy was the strongest predictor in the multivariable analysis. Its association with postoperative edema increased with retinopathy severity, while higher A1c was an additional predictor.
What was reported after glaucoma shunt surgery?
Patients with preoperative A1c above 8.4% had a five-year hazard ratio of 1.93 for blebitis or endophthalmitis compared with patients below 7.0%. The 7.0%-8.4% group did not have a statistically significant increase. The study was observational.
Should patients delay surgery to lower A1c?
The studies do not establish that delaying surgery or lowering A1c reduces these risks, and they do not set a threshold for postponement. Patients should discuss their individual risks and care plan with their qualified eye-care and medical professionals.
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